In recent months vandals have desecrated Jewish cemeteries in Rochester, N.Y., above, Philadelphia and a St. Louis suburb. Anti-Semitic incidents also have been on the rise on college campuses, and Jewish schools and community centers in the United States have received dozens of hoax bomb threats. Anti-Jewish incidents have risen in some European countries as well. (AFP/Getty Images/Gretchen Stumme)

In the run-up to the presidential election and afterward, the United States has experienced disturbing outbreaks of anti-Semitism, including a spate of incidents on more than 100 college campuses, where white supremacists have been distributing anti-Semitic fliers and openly recruiting adherents. Some human rights and Jewish activists say President Trump has emboldened right-wing hostility toward Jews, but others say such charges are unjustified. Defining anti-Semitism is controversial. Members of Congress and state legislators want to codify a definition that would include opposition to Israel's existence. But pro-Palestinian and civil liberties groups say that would violate free-speech rights. A similar debate is playing out in Europe, where some countries have seen a rise in deadly attacks on Jews in recent years, often by radicalized Muslims, such as the 2015 terrorist attack on a kosher grocery in Paris. Paradoxically, growing anti-Muslim attitudes in countries experiencing an influx of refugees have also spurred more prejudice against Jews — the target of history's longest hatred.